Electrical transformer



Nov. 11, 1947. D. o. SCHWENNESEN ELECTRICAL TRANSFORMEfi Filed Dec. 20,1945 F rm R 0 I Z 0 5 a. mm R 6 H wk 5? 6 6 ww m m 4/ mp 1 0a ww u V w QH A j a w 0 7 w J 9/ &w "n W AP! 6 N mw MW 0] m Moi] n Patented Nov..11,1947 2,430,738 ELECTRICAL TRANSFORMER Donald 0. Schwennesen, Chicago,111., assignor to Essex Wire Corporation, Detroit, Mich., a corporationof Michigan Application December 20, 1945, Serial No. 636,241

2 Claims.

This invention relates to an electrical apparatus and particularly to anaudio frequency transformer for use in plate circuit modulation. Thetransformer primary is adapted to be energized from push-pull amplifyingmeans, while the secondary is adapted to be connected in the platecircuit of a modulating stage for the purpose of modulating a suitableradio frequency carrier.

The transformer hereinafter described is particularly adapted forhandling a broad band of audio frequencies for high fidelity. As is wellknown, in audio-frequency transformers particularly for use overextended frequency ranges, capacitance to ground in the windings exert asubstantial influence on the operation of the transformer. This isparticularly true where transformers have primary and secondary windingsof substantial size and have large potential differences impressedacross said windings. The capacitance to ground distributed over variousparts of the transformer creates parasitic resonant circuits and impartsundesirable peaks and characteristics to the transformer.

The above problems inherent in an audio-frequency transformer areparticularly aggravated in the case of a transformer for use in platecircuit modulation. In such a modulating system, the transformer outputpotential must vary over substantial values. Thus, the secondary of atransformer used in plate circuit modulation in herently involvesmassive construction with capacitance to ground normally distributedover large parts of the structure.

In order to provide a transformer having an extended audio frequencycharacteristic curve, the invention hereinafter described may beutilized. In accordance with this invention, both the primary andsecondary windings are sub-divided. These sub-divided windings are soconnected and the direction of winding is so chosen that the effects ofcapacitance to ground throughout both the primary and secondary windingsare concentrated. Thus, any parasitic resonance effects are concentratedinto what might-be-termed a single parasitic circuit. The effects may becompensated in any desired manner.

The single figure in the drawing shows a transformer wound in accordancewith this invention and diagrammatically indicates the various circuitconnections to the transformer windings.

Transformer I is provided with shell core II in accordance withcustomary practice. Core ll may be made of suitable laminations with thedimensions of the various legs of the core suitably proportioned inaccordance with well-known I5 having inner terminal practice. The coreitself may be split at any desired number of places for permittingassembly of the core around the windings, or the core may be of thetypeusing continuous coiled strips of metal. Since the core is no part ofthis invention, further details are not deemed necessary.

Core II has central leg l2 around which the various windings aredisposed. Thus, immediately adjacent leg I2 is one part of secondarywinding l6 and outer terminal IT. The terms inner and outer with respectto terminals indicates respectively the position of the terminal withrespect to leg l2. The inner terminal will always be the beginning ofthe winding, while the outer terminal will always be the end of thatparticular winding. The direction in which the wire is wound isindicated by plus and minus signs. Thus, a plus sign may mean that thewire is wound clockwise for example, in which case the minus sign willhave the wire wound in reverse fashion. If desired, the same effects maybe obtained by winding all coils in the same direction and reversing thewinding.

Portion l5 of the secondary winding extends the full length of thetransformer. Around winding 15 are primary winding portions l8 and I9.It will be noted that primary portions l8 and I9 are side by side.Windings I8 and I9 have inner terminals 20 and 2| and outer terminals22and 23 respectively. The next windings are also primary windings 25and 26. These two windings are side by side with 25 being over l8 and 26being over 19. Windings 25 and 26 have inner terminals 21 and 28 andouter terminals 29 and 30. Around windings 25 and 26 is electrostaticshield 3|. The final winding is secondary portion 32, this extending thefull extent of the transformer. Secondary 32 has inner terminal 33 andouter terminal 34. An outer electrostatic shield for the entiretransformer may be provided.

Secondary windings l5 and 32 are preferably equal with regard to thenumber of layers of wire. However, this may be varied within widelimits. The same is true of primary windings l8 and IS, on the one hand,and primary windings 25 and 26, on the other hand. Primary windings l8vand 25 preferably have the same number of turns. Similarly, primarywindings l9 and 26 also have the same number of turns, this number beingthe same as the number of turns for primary windings l8 and 25.

Each Winding has the wire wound from the inner terminal to the outerterminal thereof in the direction, as viewed from the end where theinner terminal is, corresponding to the algebraic sign. Thus, secondarywinding I! may have the wire going clockwise (or positive) as viewedfrom the left-hand side of the transformer where inner terminal i6 isprovided. Looking at primary winding i8 from inner terminal 20, the wirealso goes in a clockwise direction around secondary l5. Looking atprimary I! from inner terminal 2|, the wire goes in a counter-clockwisedirection.

Considering primary 25, the wire goes counterclockwise from innerterminal 21. Primary 26 has the wir going in a clockwise direction whenviewed from inner terminal 28. Secondary 32 has the wire going clockwiseas seen from inner terminal 33.

As seen from say the left side of transformer it! in the drawing andconsidering the direction of the wire from the inner terminal to theouter terminal, windings l9 and 25 have what mightbe-termed a positivedirection, while windings l8 and 26 have a negative direction. Windingsl and 32 have the same sign, here negative. They can both be positive ifdesired.

In all cases, all primary winding portions as connected are magneticallyadditive. The same is true for the secondary winding portions.

It is also possible to have all windings wound in the same directionduring winding and have certain portions disposed in the transformer inreversed relation.

As is clearly shown in the drawing, inner terminal l6 and outer terminal34 of the secondary windings are connected together. Outer terminals 22and 23 of the primary windings are crossconnected to inner terminals 26and 28 respectively of the remaining primary windings.

It is understood that suitable insulation between windings may beprovided. The electrostatic shields and frame are suitably grounded-Inner terminals 20 and 2| lead 31 going to any suitable source of B pluspotential. Outer terminals 29 and 30 of the primary windings areconnected by leads 38 and 39 to the output of a push-pull amplifier.This push-pull amplifier may be considered as a source of modulatingaudio frequency input to transformer i0.

Outer terminal I! of the secondary is connected a suitable source of Bplus potential, while are connected to inner terminal 23 of thesecondary may be connected through a suitable radi frequency choke 40 tothe anode of modulator tube or stag ll. Modulator ll may have grid 42supplied with suitable radio frequency carrier waves. Tube 4| hascathode 0 between which electrode and anode are condensers 4i and 46connected in series. Across condenser 43 is primary 41 of radiofrequency transformer 4| whose secondary 49 has modulated radiofrequency potentials. Condenser 48 may be variable to tune winding 41and select the proper modulated frequency output.

What is claimed is:

1. A wide-band audio frequency transformer comprising a ferromagneticcore. a first fulllength secondary winding, second and third primarywindings disposed side by side around said first winding, fourth andfifth primary winding; disposed side by side over the second and thirdwindings respectively, an lectrostatic shield over said fourth and fifthwindings, a sixth full-length secondary winding similar to the firstwinding over said electrostatic shield, all of said windings havinginner and outer terminals respectively and connected as follows: theinner second tov the inner third to provide one common primary terminal,the outer second to the inner fifth, the outer third to th inner fourth,the outer terminals of the fourth and fifth being free for connection ofthe primary to an external circuit, the inner first to the outer sixthleaving the outer first and inner sixth as external secondaryconnections, all primary windings being magnetically aiding, thesecondary windings also being magnetically aiding.

2. The transformer of claim 1 wherein said core is of the shell type.

DONALD O. SCHWENNESEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,390,800 Nadsen Dec. 11, 19452,038,992 Chaifee Apr. 28, 1936

